code: def test_mixin(base):
      """Test _MockEstimatorMixin is valid for all sktime estimator base classes."""
  
      class _DummyClass(base, _MockEstimatorMixin):
          def __init__(self):
              super().__init__()
  
          def _fit(self):
              """Empty method, here for testing purposes."""
              pass
  
          def _predict(self):
              """Empty method, here for testing purposes."""
              pass
  
          def _score(self):
              """Empty method, here for testing purposes."""
              pass
  
      dummy_instance = _DummyClass()
      assert hasattr(dummy_instance, "log")
      dummy_instance.add_log_item(42)
      assert hasattr(dummy_instance, "_MockEstimatorMixin__log")
  
file_path: sktime/sktime/utils/estimators/tests/test_base.py
imports: import pytest
  from pandas.testing import assert_series_equal
  from sktime.classification.base import BaseClassifier
  from sktime.clustering.base import BaseClusterer
  from sktime.datasets import load_airline
  from sktime.forecasting.base import BaseForecaster
  from sktime.forecasting.naive import NaiveForecaster
  from sktime.transformations.base import BaseTransformer
  from sktime.transformations.series.boxcox import BoxCoxTransformer
  from sktime.utils.estimators import make_mock_estimator
  from sktime.utils.estimators._base import _method_logger, _MockEstimatorMixin
label_desc: Use image node_id 1 for calling a global function with example usage: test_mixin(base) without return types